Aquarium heater



FIG. 1 is a front elevational view of an aquarium heater, showing my new design;

FIG. 2 is a right side elevational view thereof;

FIG. 3 is a rear elevational view thereof;

FIG. 4 is a left side elevational view thereof;

FIG. 5 is a top plan view thereof;

FIG. 6 is a bottom plan view thereof.

The conventional electrical cord has been shown fragmentarily in FIGS. 1-4 for ease of illustration. 

The ornamental design for an aquarium heater, as shown and described. 